A mobile charging PCB/sub-board falls under several key categories, including **power management**, **charging circuitry**, and **safety protection**. These boards house components for voltage regulation, current control, and overcharge protection, ensuring efficient and safe charging. They are designed for integration with **USB charging interfaces**, **wireless charging** modules, and **fast charging technologies** like Quick Charge or Power Delivery. The sub-boards are typically compact, designed to fit into mobile devices, and incorporate safety features such as **thermal protection**, **overvoltage protection**, and **short circuit prevention**. They play a critical role in maintaining battery health and device functionality during charging.